In response to requirements for space saving in use of reflection type screens and blackboards or whiteboards, and for more efficient presentation, various boards having both of these two functions have been proposed and used in practice (for example, Japanese Patent Laid-open Publication (Kokai) Nos. 6-27532, 9-230506, 10-287091 and so forth).
In general, a writing board such as a whiteboard is required to have a smooth surface so that a user can write with a water-based pen and erase the writing. However, a reflection type screen is required to reflect light without glare so that the reflected light can be easily viewed as an image.
Therefore, a conventional board used as both a reflection type screen and a writing board is imparted with writability and erasability for water-color ink by providing a substrate with a resin layer such as an aromatic polyester or fluororesin having low wettability or easy erasability for a water-color ink, and the board surface is made with reduced gloss to suppress glare. In order to reduce gloss of the board surface, a pigment and a light diffusion agent are usually incorporated into the resin layer.
However, when a layer containing pigments or the like is formed on a surface, a problem arises that an ink easily penetrates between pigment particles, and that the ink, once penetrated, cannot be erased even when the surface is wiped. Moreover, when pigments are present, attainment of proper unevenness (protrusions and depressions) on the board surface is difficult, and it is difficult to form unevenness providing both ink erasability and anti-glare on the surface.
In particular, the phenomenon whereby an image is hard to see due to the brightness in the center of the light-shed area (so-called hot spot) is problematic in a reflection type screen used with modern projectors having high optical power. A conventional writing board also serving as a reflection type screen has the problem that this hot spot cannot be completely eliminated and hence a projected image is hard to see.